by Neil Bauman, Ph.D.
Right now we are in a transition between the existing analog TV transmission standard and the new digital TV standard. On February 17, 2009 here in the USA, all analog TV transmissions will cease, and we will enter the 100% digital TV transmission age. (Don’t confuse digital TV with high definition (HD) TV.)
This raises a number of questions concerning how captions will work with digital TVs, set top boxes, converter boxes, cable boxes, etc.
Because it was not clearly thought through from the beginning of the planning phase, this is more complicated that it needed to be is. To explain some of the things of which you need to be aware, here is my friend Steve Barber. He writes:
There are several advantages of digital captions, such as being able to control the color, size, transparency and location of the captions (depending on your equipment). In addition, captions should never garble if you’ve got a digital signal.
However, things aren’t as simple as they used to be. Originally, TVs only had one input (the antenna) so hooking them up wasn’t much of a technical challenge. Then, along came cable, satellite, VCRs, DVDs, set-top boxes, home theater equipment, caption decoder boxes (later replaced by chips in the TV) and things got more complicated.
For years, TVs have had various places to plug in all that stuff—coax connectors for the satellite and cable, RCA (composite) jacks for various other sources, and S-video on some TVs for certain connections. Even so, since 1993, the captions were normally decoded by a chip in the TV, no matter what the source.
Now, in addition to the above connectors, digital TVs also have HDMI connectors (which are supposed to allow optimum picture and audio quality).
Here’s where it gets more interesting. Captions are no longer analog signals buried in the invisible raster scan of the analog TV signal. Digital captions are stored in the signal as bits. The problem is that HDMI connectors only carry the video and audio signals. They can’t carry the digital captions. Thus, one problem is how to get captions if you use an HDMI connector from a converter box or other source.
The answer is that converter and set-top boxes will have caption decoder chips built-in, just like your TV has today. Thus, if you use an HDMI connector, you’ll have to turn on the captions in the set-top box or another source, and have it insert the captioned text into the image, which the HDMI connector can then transmit.
Alternatively, you can connect your TV from various sources with one of the other connector types, and then use your TV’s decoder chip to decode the signal. Depending on the connector, the signal may not be as wonderful as it could be, but also, depending on your TV, it may not matter. Most of the great TVs you see in the store are being run on composite connections, not HDMI. Fortunately, on most TVs you’d not be able to tell the difference anyway.
DVDs and VCRs present another problem. A few have their own tuners, and therefore have their own caption decoders built in. Thus, you may be able to use that caption decoder if you can’t otherwise get the undecoded captions to your TV.
A word about DVDs: DVDs frequently have both closed captions and subtitles. Some DVDs only have one or the other. Thus, you have to know which is which, and how to get them displayed. Also, you have to make sure they are not both displayed at once! Closed Captions have to be decoded to be displayed. Subtitles are an option on the DVD’s program menu.
If you want to see the captions encoded on a DVD, you’ll either need to have a DVD Player that has its own tuner and caption decoder (there aren’t many of them), or you mustn’t connect to your TV via HDMI. If you are connected by HDMI, you’ll need to decode the captions first in the player so they are then incorporated as part of the image which then can go via HDMI.
Subtitles are probably going to be more common on DVDs because the DVD players will let them be put in the image if you select them. Thus, if the DVD has subtitles, it’s probably the easiest solution for captions when playing a DVD.
Originally Closed Captions were designed for people who couldn’t hear, so they included environmental sounds, such as “dog barks” or “toilet flushes” as well as what was spoken. Subtitles (remember silent films or foreign films?) were originally for people who could hear, so they didn’t include environmental sounds. Even when they first appeared on DVDs, subtitles didn’t include environmental sounds. As a result, many deaf or hard of hearing people preferred the Closed Captions.
Fortunately, recent DVDs are starting to include “Subtitles for the Hearing Impaired” (SDH) and to include the environmental sounds. In the future, I think we’ll see DVDs with SDH instead of Closed Captions. That may simplify getting captions displayed when you’re using a DVD.
Your set-top box for cable or satellite, or a digital to analog converter box, will have menus (and maybe a remote button) for controlling the caption decoder in the set top box. Thus, for most people when watching TV through one of those, you’d turn off your TV’s decoder and turn on the decoder in the set top box. This should be reliable and easy, but you’ll have to understand which devices have decoders, and how to turn them on or off. Once you’ve set them up, it should be fine even though there are so many more options to understand than in the old days.
You can find a bunch of good information at the North Carolina Hearing Loss Association website Steve maintains.